Printed circuit boards route signals and power through electronic devices, providing both mechanical and electrical connections. Conductive pathways or tracks are etched onto a copper sheet to provide the basic layout of PCBs. PCBs are used in almost all electronic devices. They are sometimes confused with printed wiring boards, or PWBs, but unlike PWBs, PCBs have circuit elements manufactured into the nonconductive substrate of the board.
Before PCBs became widespread, electric connections were established through point-to-point wiring. However, as the wiring insulation aged and cracked, frequent failures occurred at wire junctions. Wire wrapping improved the durability and duration of these connections. As demand for electronics increased, the pressure to reduce the size and cost of products led to the development of the PCB.
PCBs are made out of various components layered onto each other and laminated together. The base material is usually fiberglass of various thicknesses. Cheaper versions use epoxies or phenolics, but the lower price tag comes at the cost of reduced durability. The next layer is a thin sheet of copper, followed by the soldermask. A silkscreen is not strictly necessary but allows users to attach labels to each pin or LED.
Designs for the modern PCB began in the early 1900s, though these methods would not converge until the 1980s.